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Nickel and copper are often obtained by electrowinning. These metals have some noble character, which enables their soluble cationic forms to be reduced to their pure metallic form at mild applied potentials applied between the cathode and the anode. | 1 | Applied and Interdisciplinary Chemistry |
The unique features of NICE-OHMS, in particular its high sensitivity, imply that it has a large potential for a variety of applications. First developed for frequency standard applications, with an astonishing detectability of 10 cm, it has later been used for spectroscopic investigations as well as chemical sensing and trace species detection, with detectabilities in the 10 - 10 cm range. However, although the NICE-OHMS technique has shown to possess an extremely high detectability, it has so far only sparsely been developed towards trace gas analysis.
One of the biggest hurdles for implementation of the NICE-OHMS technique is indisputably the locking of the frequency of the laser to that of a cavity mode. Although the requirements for the performance of the lock are less stringent than for other direct cw-CEAS techniques (due to the noise-immune principle), the laser frequency still has to be kept locked within the cavity mode during signal acquisition, i.e. it should follow the mode while the cavity is scanned, including a possible wavelength modulation. It can be difficult to achieve these goals if the free-running linewidth of the laser is significantly larger than the cavity mode width and if the laser is prone to sudden frequency excursions due to technical noise from the surroundings. This is usually the case when working with medium- or high finesse cavities (with transmission mode widths in the low kHz range) and standard types of lasers, e.g. external cavity diode lasers (ECDLs), with free-running linewidths in the MHz range. Electronic feedback loops with high bandwidths (typically a few MHz) and high gain are then needed to couple a substantial amount of the laser power into a cavity mode and to ensure stable performance of the lock.
With the advent of narrow linewidth fiber lasers, the problems connected to laser locking can be significantly reduced. Fiber lasers with free-running linewidths as narrow as 1 kHz (measured over a fraction of a second), thus two to three orders of magnitude below those of ECDLs, are available today. Evidently, this feature simplifies the feedback electronics (bandwidths as low as 10 kHz are sufficient) and the locking procedure considerably. Moreover, the design and working principle of fiber lasers make them less affected by external disturbances, e.g. mechanical and acoustical noise, than other solid state lasers or ECDLs. In addition, the availability of integrated-optics components, such as fiber based electro-optic modulators (fiber EOMs), offers the possibility to further reduce the complexity of the setup. The first realizations of a NICE-OHMS system based upon a fiber laser and a fiber EOM have recently been demonstrated. It was shown that CH could be detected down to 4.5•10 atm (4.5 ppt) with an instrumentation that is very sturdy. It is clear that this has brought NICE-OHMS a step closer to become a practically useful technique for ultra-sensitive trace species detection! | 0 | Theoretical and Fundamental Chemistry |
LTR retrotransposons came about later than non-LTR retrotransposons, possibly from an ancestral non-LTR retrotransposon acquiring an integrase from a DNA transposon. Retroviruses gained additional properties to their virus envelopes by taking the relevant genes from other viruses using the power of LTR retrotransposon.
Due to their retrotransposition mechanism, retrotransposons amplify in number quickly, composing 40% of the human genome. The insertion rates for LINE1, Alu and SVA elements are 1/200 – 1/20, 1/20 and 1/900 respectively. The LINE1 insertion rates have varied a lot over the past 35 million years, so they indicate points in genome evolution.
Notably a large number of 100 kilobases in the maize genome show variety due to the presence or absence of retrotransposons. However since maize is unusual genetically as compared to other plants it cannot be used to predict retrotransposition in other plants.
Mutations caused by retrotransposons include:
* Gene inactivation
* Changing gene regulation
* Changing gene products
* Acting as DNA repair sites | 1 | Applied and Interdisciplinary Chemistry |
John Douglas Eshelby FRS (21 December 1916 – 10 December 1981) was a scientist in micromechanics. He made significant contributions to the fields of defect mechanics and micromechanics of inhomogeneous solids for fifty years, including important aspects of the controlling mechanisms of plastic deformation and fracture. | 1 | Applied and Interdisciplinary Chemistry |
Total CO emissions from energy use were 5% below their 1990 level in 2007. Over the period 1990–2007, CO emissions from energy use have decreased on average by 0.3%/year although the economic activity (GDP) increased by 2.3%/year. After dropping until 1994 (−1.6%/year), the CO emissions have increased steadily (0.4%/year on average) until 2003 and decreased slowly again since (on average by 0.6%/year). Total CO emissions per capita decreased from 8.7 t in 1990 to 7.8 t in 2007, that is to say a decrease by 10%.
Almost 40% of the reduction in CO intensity is due to increased use of energy carriers with lower emission factors.
Total CO emissions per unit of GDP, the “CO intensity”, decreased more rapidly than energy intensity: by 2.3%/year and 1.4%/year, respectively, on average between 1990 and 2007.
However, while the reports from 2007 suggest that the CO emissions are going down recent studies find that the global emissions are rapidly escalating. According to the Climate Change 2022 Mitigation of Climate Change report, conducted by the IPCC, it states that it 2019 the world emissions output was 59 gigatonnes. This shows that global emissions has grown rapidly, increasing by about 2.1% each year compared from the previous decade.
The Commodity Exchange Bratislava (CEB) has calculated carbon intensity for Voluntary Emissions Reduction projects carbon intensity in 2012 to be 0.343 tn/MWh.
According to data from the European Commission, in order to achieve the EU goal of decreasing greenhouse gas emissions by at least 55% by 2030 compared to 1990, EU-based energy investment has to double from the previous decade to more than €400 billion annually this decade. This includes the roughly €300 billion in yearly investment required for energy efficiency and the roughly €120 billion required for power networks and renewable energy facilities. | 1 | Applied and Interdisciplinary Chemistry |
In 1955, Time magazine reported:
"In Manhattan, Psychiatrist Harold A. Abramson of the Cold Spring Harbor Biological Laboratory has developed a technique of serving dinner to a group of subjects, topping off the meal with a liqueur glass containing 40 micrograms of LSD."
This mention in America's most popular newsweekly is noteworthy because Abramson was not a psychiatrist or even a psychologist, but was an allergist who was a key participant in the CIA MK-ULTRA mind-control program. | 1 | Applied and Interdisciplinary Chemistry |
The primary role of CTCF is thought to be in regulating the 3D structure of chromatin. CTCF binds together strands of DNA, thus forming chromatin loops, and anchors DNA to cellular structures like the nuclear lamina. It also defines the boundaries between active and heterochromatic DNA.
Since the 3D structure of DNA influences the regulation of genes, CTCF's activity influences the expression of genes. CTCF is thought to be a primary part of the activity of insulators, sequences that block the interaction between enhancers and promoters. CTCF binding has also been both shown to promote and repress gene expression. It is unknown whether CTCF affects gene expression solely through its looping activity, or if it has some other, unknown, activity. In a recent study, it has been shown that, in addition to demarcating TADs, CTCF mediates promoter–enhancer loops, often located in promoter-proximal regions, to facilitate the promoter–enhancer interactions within one TAD. This is in line with the concept that a subpopulation of CTCF associates with the RNA polymerase II (Pol II) protein complex to activate transcription. It is likely that CTCF helps to bridge the transcription factor-bound enhancers to transcription start site-proximal regulatory elements and to initiate transcription by interacting with Pol II, thus supporting a role of CTCF in facilitating contacts between transcription regulatory sequences. This model has been demonstrated by the previous work on the beta-globin locus. | 1 | Applied and Interdisciplinary Chemistry |
In the silicification of woods, silica dissolves in hydrothermal fluid and seeps into lignin in cell walls. Precipitation of silica out of the fluids produces silica deposition within the voids, especially in the cell walls. Cell materials are broken down by the fluids, yet the structure remains stable due to the development of minerals. Cell structures are slowly replaced by silica. Continuous penetration of siliceous fluids results in different stages of silicification ie. primary and secondary. The loss of fluids over time leads to the cementation of silicified woods through late silica addition.
The rate of silicification depends on a few factors:
1) Rate of breakage of original cells
2) Availability of silica sources and silica content in the fluid
3) Temperature and pH of silicification environment
4) Interference of other diagenetic processes
These factors affect the silicification process in many ways. The rate of breakage of original cells controls the development of the mineral framework, hence the replacement of silica. Availability of silica directly determines the silica content in fluids. The higher the silica content, the faster silicification could take place. The same concept applies to the availability of hydrothermal fluids. The temperature and pH of the environment determine the condition for silicification to occur. This is closely connected to the burial depth or association with volcanic events. Interference of other diagenetic processes could sometimes create disturbance to silicification. The relative time of silicification to other geological processes could serve as a reference for further geological interpretations. | 0 | Theoretical and Fundamental Chemistry |
Many phosphatases are promiscuous with respect to substrate type, or can evolve quickly to change substrate. An alternative structural classification notes that 20 distinct protein folds have phosphatase activity, and 10 of these contain protein phosphatases.
* The CC1 fold is the most common, and includes tyrosine-specific (PTP), dual-specific (DSP) and even lipid-specific (PTEN) families.
* The major serine/threonine-specific folds are PPM (PP2C) and PPPL (PPP).
* The only known histidine phosphatases is in the PHP fold.
* Other folds encode phosphatases that act on various combination of pSer, pThr, pTyr, and non-protein substrates (CC2, CC3, HAD, HP, AP, RTR1). | 1 | Applied and Interdisciplinary Chemistry |
Measuring the quantity of water vapor in a medium can be done directly or remotely with varying degrees of accuracy. Remote methods such electromagnetic absorption are possible from satellites above planetary atmospheres. Direct methods may use electronic transducers, moistened thermometers or hygroscopic materials measuring changes in physical properties or dimensions. | 1 | Applied and Interdisciplinary Chemistry |
Calcium stable isotopes have been used to study inputs and outputs of dissolved calcium in marine environments. For example, one study found that calcium levels have decreased between 25 and 50 percent over a 40 million year timespan, suggesting that dissolved Caoutputs have exceeded its inputs. The isotope Calcium-44 can help to indicate variations in calcium carbonate over long timespans and help explain variants in global temperature. Declines in the isotope Calcium-44 usually correlate with periods of cooling, as dissolution of calcium carbonate typically signifies a decrease in temperature. Thus, Calcium isotopes correlate with Earth's climate over long periods of time. | 1 | Applied and Interdisciplinary Chemistry |
From 1934, following the Nazi takeover, it became more and more difficult for Speter to research and publish due to his Jewish ancestry. In 1937 the German radio cancelled a planned broadcast of his public lecture. From 1939 and on he was banned completely from publishing in Germany.
Speter committed suicide on 30 June 1942. | 1 | Applied and Interdisciplinary Chemistry |
The stress tensor is related to velocity and pressure. Its actual form will depend on the specific fluid being dealt with, for the common case of incompressible Newtonian flow the stress tensor is given by
where is the pressure in the fluid, is the velocity, and is the viscosity. | 1 | Applied and Interdisciplinary Chemistry |
The oceanic carbon cycle (or marine carbon cycle) is composed of processes that exchange carbon between various pools within the ocean as well as between the atmosphere, Earth interior, and the seafloor. The carbon cycle is a result of many interacting forces across multiple time and space scales that circulates carbon around the planet, ensuring that carbon is available globally. The Oceanic carbon cycle is a central process to the global carbon cycle and contains both inorganic carbon (carbon not associated with a living thing, such as carbon dioxide) and organic carbon (carbon that is, or has been, incorporated into a living thing). Part of the marine carbon cycle transforms carbon between non-living and living matter.
Three main processes (or pumps) that make up the marine carbon cycle bring atmospheric carbon dioxide (CO) into the ocean interior and distribute it through the oceans. These three pumps are: (1) the solubility pump, (2) the carbonate pump, and (3) the biological pump. The total active pool of carbon at the Earth's surface for durations of less than 10,000 years is roughly 40,000 gigatons C (Gt C, a gigaton is one billion tons, or the weight of approximately 6 million blue whales), and about 95% (~38,000 Gt C) is stored in the ocean, mostly as dissolved inorganic carbon. The speciation of dissolved inorganic carbon in the marine carbon cycle is a primary controller of acid-base chemistry in the oceans.
Earth's plants and algae (primary producers) are responsible for the largest annual carbon fluxes. Although the amount of carbon stored in marine biota (~3 Gt C) is very small compared with terrestrial vegetation (~610 GtC), the amount of carbon exchanged (the flux) by these groups is nearly equal – about 50 GtC each. Marine organisms link the carbon and oxygen cycles through processes such as photosynthesis. The marine carbon cycle is also biologically tied to the nitrogen and phosphorus cycles by a near-constant stoichiometric ratio C:N:P of 106:16:1, also known as the Redfield Ketchum Richards (RKR) ratio, which states that organisms tend to take up nitrogen and phosphorus incorporating new organic carbon. Likewise, organic matter decomposed by bacteria releases phosphorus and nitrogen.
Based on the publications of NASA, World Meteorological Association, IPCC, and International Council for the Exploration of the Sea, as well as scientists from NOAA, Woods Hole Oceanographic Institution, Scripps Institution of Oceanography, CSIRO, and Oak Ridge National Laboratory, the human impacts on the marine carbon cycle are significant. Before the Industrial Revolution, the ocean was a net source of CO to the atmosphere whereas now the majority of the carbon that enters the ocean comes from atmospheric carbon dioxide (CO). The burning of fossil fuels and production of cement have changed the balance of carbon dioxide between the atmosphere and oceans, causing acidification of the oceans. Climate change, a result of excess CO in the atmosphere, has increased the temperature of the ocean and atmosphere (global warming). The slowed rate of global warming occurring from 2000–2010 may be attributed to an observed increase in upper ocean heat content. | 0 | Theoretical and Fundamental Chemistry |
In chemical kinetics, the entropy of activation of a reaction is one of the two parameters (along with the enthalpy of activation) which are typically obtained from the temperature dependence of a reaction rate constant, when these data are analyzed using the Eyring equation of the transition state theory. The standard entropy of activation is symbolized and equals the change in entropy when the reactants change from their initial state to the activated complex or transition state ( = change, = entropy, = activation). | 0 | Theoretical and Fundamental Chemistry |
Multimedia fugacity model is a model in environmental chemistry that summarizes the processes controlling chemical behavior in environmental media by developing and applying of mathematical statements or "models" of chemical fate.
Most chemicals have the potential to migrate from the medium to medium. Multimedia fugacity models are utilized to study and predict the behavior of chemicals in different environmental compartments.
The models are formulated using the concept of fugacity, which was introduced by Gilbert N. Lewis in 1901 as a criterion of equilibrium and convenient method of calculating multimedia equilibrium partitioning.
The fugacity of chemicals is a mathematical expression that describes the rates at which chemicals diffuse, or are transported between phases. The transfer rate is proportional to the fugacity difference that exists between the source and destination phases.
For building the model, the initial step is to set up a mass balance equation for each phase in question that includes fugacities, concentrations, fluxes and amounts. The important values are the proportionality constant, called fugacity capacity expressed as Z-values (SI unit: mol/m Pa) for a variety of media, and transport parameters expressed as D-values (SI unit: mol/Pa h) for processes such as advection, reaction and intermedia transport. The Z-values are calculated using the equilibrium partitioning coefficients of the chemicals, Henry's law constant and other related physical-chemical properties. | 0 | Theoretical and Fundamental Chemistry |
The degree distribution describes the number of proteins that have a certain number of connections. Most protein interaction networks show a scale-free (power law) degree distribution where the connectivity distribution P(k) ~ k with k being the degree. This relationship can also be seen as a straight line on a log-log plot since, the above equation is equal to log(P(k)) ~ —y•log(k). One characteristic of such distributions is that there are many proteins with few interactions and few proteins that have many interactions, the latter being called "hubs". | 1 | Applied and Interdisciplinary Chemistry |
Enantioselective dioxirane oxidations may rely on chiral, non-racemic dioxiranes, such as Shis fructose-based dioxirane. Enantioselective oxidation of meso-diols with Shis catalyst, for instance, produces chiral α-hydroxy ketones with moderate enantioselectivity. | 0 | Theoretical and Fundamental Chemistry |
Small redox proteins such as cytochromes and ferredoxins can be investigated on condition that their electroactive coverage (the amount of protein undergoing direct electron transfer) is large enough (in practice, greater than a fraction of pmol/cm).
Electrochemical data obtained with small proteins can be used to measure the redox potentials of the protein's redox sites, the rate of electron transfer between the protein and the electrode, or the rates of chemical reactions (such as protonations) that are coupled to electron transfer. | 0 | Theoretical and Fundamental Chemistry |
Electroplasticity, describes the enhanced plastic behavior of a solid material under the application of an electric field. This electric field could be internal, resulting in current flow in conducting materials, or external. The effect of electric field on mechanical properties ranges from simply enhancing existing plasticity, such as reducing the flow stress in already ductile metals, to promoting plasticity in otherwise brittle ceramics. The exact mechanisms that control electroplasticity vary based on the material and the exact conditions (e.g., temperature, strain rate, grain size, etc.). Enhancing the plasticity of materials is of great practical interest as plastic deformation provides an efficient way of transforming raw materials into final products. The use of electroplasticity to improve processing of materials is known as electrically assisted manufacturing. | 0 | Theoretical and Fundamental Chemistry |
Oxygen comes in three variants, but the O is so rare that it is very difficult to detect (~0.04% abundant). The ratio of O/O in water depends on the amount of evaporation the water experienced (as O is heavier and therefore less likely to vaporize). As the vapor tension depends on the concentration of dissolved salts, the O/O ratio shows correlation on the salinity and temperature of water. As oxygen gets built into the shells of calcium carbonate secreting organisms, such sediments provide a chronological record of temperature and salinity of the water in the area.
Oxygen isotope ratio in atmosphere varies predictably with time of year and geographic location; e.g. there is a 2% difference between O-rich precipitation in Montana and O-depleted precipitation in Florida Keys. This variability can be used for approximate determination of geographic location of origin of a material; e.g. it is possible to determine where a shipment of uranium oxide was produced. The rate of exchange of surface isotopes with the environment has to be taken in account.
The oxygen isotopic signatures of solid samples (organic and inorganic) are usually measured with pyrolysis and mass spectrometry. Researchers need to avoid improper or prolonged storage of the samples for accurate measurements. | 0 | Theoretical and Fundamental Chemistry |
The space groups with given point group are numbered by 1, 2, 3, ... (in the same order as their international number) and this number is added as a superscript to the Schönflies symbol for the corresponding point group. For example, groups numbers 3 to 5 whose point group is C have Schönflies symbols C, C, C.
While in case of point groups, Schönflies symbol defines the symmetry elements of group unambiguously, the additional superscript for space group doesn't have any information about translational symmetry of space group (lattice centering, translational components of axes and planes), hence one needs to refer to special tables, containing information about correspondence between Schönflies and Hermann–Mauguin notation. Such table is given in List of space groups page. | 0 | Theoretical and Fundamental Chemistry |
In a bell and spigot joint one end of the pipe stick is flared, termed the bell or socket, to enable the opposite end of the next stick, the spigot end, to be inserted to create a joint. The gaps in these joints were stuffed with oakum or yarn to retain molten-lead, which solidified into a waterproof joint. This was a labor-intensive operation, and the quality of the seal was dependent on the skill of the laborer.
Mechanical joints were made by bolting a movable follower ring on the spigot close to the corresponding bell, which compressed a gasket in between. Many water pipes today use mechanical joints, since they are easily made and do not require special skills to install. This type of joint also allows some deflection to occur without sacrificing joint integrity, so that minor alignment adjustments can be made during installation, and the joints retain their integrity when subjected to limited subsidence. Typical joint deflections at mechanical joints today range anywhere from 3 to 5 degrees.
Ball-and-socket joints introduced more "rounded" sockets, allowing a relatively large amount of deflection at each joint. This type of joint, still in use today, was considered a special-purpose joint, and has been used primarily in both submerged and mountainous terrain. This type of joint can typically allow around 15 degrees of deflection at each joint, making snaking of the pipe possible. The advantage of this joint type was that it was quicker than bell and spigot joints, and did not require special skills or tools to install.
Push-on joints, developed in the mid 1950s, allowed a quicker and relatively non-skilled method of jointing pipe. This joint consisted of a bell with a recessed groove which held a rubberized gasket. A lubricated beveled spigot section can be pushed into this joint with care, as not to roll the rubberized gasket, and once installed became watertight. This type of jointing system is popular today with ductile iron and polyvinyl chloride (PVC) pipes. | 1 | Applied and Interdisciplinary Chemistry |
In traditional mineral exploration and archaeological work, grid pegs placed by theodolite and tape measure were used to define the survey area. Some UXO surveys used ropes to define the lanes. Airborne surveys used radio triangulation beacons, such as Siledus.
Non-magnetic electronic hipchain triggers were developed to trigger magnetometers. They used rotary shaft encoders to measure distance along disposable cotton reels.
Modern explorers use a range of low-magnetic signature GPS units, including real-time kinematic GPS. | 0 | Theoretical and Fundamental Chemistry |
Starting with a technique commonly used to deposit molecules on a solid surface, Langmuir–Blodgett deposition, scientists are able to assemble phospholipid membranes of arbitrary complexity layer by layer. These artificial phospholipid membranes support functional insertion both of purified and of in situ expressed membrane proteins. The technique could help astrobiologists understand how the first living cells originated. | 0 | Theoretical and Fundamental Chemistry |
After short stays at NRC and Acadia University, Yu was appointed to the Department of Chemistry at Simon Fraser University in 2001 as an assistant professor and promoted to a tenured full professor in 2009. He is now a principal investigator of the CFI-funded Centre for Nanomaterials and Microstructures (4D LABS) and an associate member of the Department of Molecular Biology and Biochemistry, both at SFU. Yu has been perusing his cutting-edge research on solving fundamental problems that have direct impact on applied analytical science and technology. His innovation of adapting mobile electronics (office scanners, disc players, and now smartphones) for portable molecular analysis and his contribution to the de novo construction of ultrasensitive electronic biosensors for disease markers, lead to the possibility of performing many quantitative chemical analysis on-site and biomedical diagnostic tests at point-of-care settings. He has published more than 160 peer-reviewed articles and holds/filed 14 national/international patents. | 0 | Theoretical and Fundamental Chemistry |
Adrenaline stimulates photocytes to emit light for many species of fish. It is believed that sympathetic nervous impulses provide the stimulus that causes photocytes to emit light. | 1 | Applied and Interdisciplinary Chemistry |
Levonorgestrel stimulates the proliferation of MCF-7 breast cancer cells in vitro, an action that is independent of the classical PRs and is instead mediated via the progesterone receptor membrane component-1 (PGRMC1). Certain other progestins act similarly in this assay, whereas progesterone acts neutrally. It is unclear if these findings may explain the different risks of breast cancer observed with progesterone and progestins in clinical studies. | 0 | Theoretical and Fundamental Chemistry |
The Wnt signaling pathways are critical in cell-cell signaling during normal development and embryogenesis and required for maintenance of adult tissue, therefore it is not difficult to understand why disruption in Wnt signaling pathways can promote human degenerative disease and cancer.
The Wnt signaling pathways are complex, involving many different elements, and therefore have many targets for misregulation. Mutations that cause constitutive activation of the Wnt signaling pathway lead to tumor formation and cancer. Aberrant activation of the Wnt pathway can lead to increase cell proliferation. Current research is focused on the action of the Wnt signaling pathway the regulation of stem cell choice to proliferate and self renew. This action of Wnt signaling in the possible control and maintenance of stem cells, may provide a possible treatment in cancers exhibiting aberrant Wnt signaling. | 1 | Applied and Interdisciplinary Chemistry |
Uzer was Alexander von Humboldt-Stiftung Foundation Fellow in 1993–1994 at
Max Planck Institute, Munich.
Uzer is of Turkish origin and was also awarded the prestigious Science award for his contributions to physics from the Scientific and Technological Research Council (TÜBİTAK) [http://www.biltek.tubitak.gov.tr/oduller_en/previous_science.htm] in 1998. | 0 | Theoretical and Fundamental Chemistry |
Natural food and all-natural food are terms in food labeling and marketing with several definitions, often implying foods that are not manufactured by processing. In some countries like the United Kingdom, the term "natural" is defined and regulated; in others, such as the United States, the term natural is not enforced for food labels, although there is USDA regulation of organic labeling.
The term is assumed to describe foods having ingredients that are intrinsic to an unprocessed food. | 1 | Applied and Interdisciplinary Chemistry |
Organic thiocyanates are organic compounds containing the functional group RSCN. the organic group is attached to sulfur: R−S−C≡N has a S–C single bond and a C≡N triple bond.
Organic thiocyanates are valued building blocks. They allow to access efficiently various sulfur containing functional groups and scaffolds. | 0 | Theoretical and Fundamental Chemistry |
Broadening in laser physics is a physical phenomenon that affects the spectroscopic line shape of the laser emission profile. The laser emission is due to the (excitation and subsequent) relaxation of a quantum system (atom, molecule, ion, etc.) between an excited state (higher in energy) and a lower one. These states can be thought of as the eigenstates of the energy operator. The difference in energy between these states is proportional to the frequency/wavelength of the photon emitted. Since this energy difference has a fluctuation, then the frequency/wavelength of the "macroscopic emission" (the beam) will have a certain width (i.e. it will be "broadened" with respect to the "ideal" perfectly monochromatic emission).
Depending on the nature of the fluctuation, there can be two types of broadening. If the fluctuation in the frequency/wavelength is due to a phenomenon that is the same for each quantum emitter, there is homogeneous broadening, while if each quantum emitter has a different type of fluctuation, the broadening is inhomogeneous.
Examples of situations where the fluctuation is the same for each system (homogeneous broadening) are natural or lifetime broadening, and collisional or pressure broadening. In these cases each system is affected "on average" in the same way (e.g. by the collisions due to the pressure).
The most frequent situation in solid state systems where the fluctuation is different for each system (inhomogeneous broadening) is when because of the presence of dopants, the local electric field is different for each emitter, and so the Stark effect changes the energy levels in an inhomogeneous way. The homogeneous broadened emission line will have a Lorentzian profile (i.e. will be best fitted by a Lorentzian function), while the inhomogeneously broadened emission will have a Gaussian profile. One or more phenomena may be present at the same time, but if one has a wider fluctuation, it will be the one responsible for the character of the broadening.
These effects are not limited to laser systems, or even to optical spectroscopy. They are relevant in magnetic resonance as well, where the frequency range is in the radiofrequency region for NMR, and one can also refer to these effects in EPR where the lineshape is observed at fixed (microwave) frequency and in a magnetic field range. | 0 | Theoretical and Fundamental Chemistry |
Human milk oligosaccharides (HMOs), also known as human milk glycans, are short polymers of simple sugars that can be found in high concentrations in human breast milk. Human milk oligosaccharides promote the development of the immune system, can reduce the risk of pathogen infections and improve brain development and cognition. The HMO profile of human breast milk shapes the gut microbiota of the infant by selectively stimulating bifidobacteria and other bacteria. | 0 | Theoretical and Fundamental Chemistry |
During normal metabolism in humans approximately 20% of the 1,3BPG produced does not go any further in the glycolytic pathway. It is instead shunted through an alternate pathway involving the reduction of ATP in the red blood cells. During this alternate pathway it is made into a similar molecule called 2,3-bisphosphoglyceric acid (2,3BPG). 2,3BPG is used as a mechanism to oversee the efficient release of oxygen from hemoglobin. Levels of this 1,3BPG will raise in a patient's blood when oxygen levels are low as this is one of the mechanisms of acclimatization. Low oxygen levels trigger a rise in 1,3BPG levels which in turn raises the level of 2,3BPG which alters the efficiency of oxygen dissociation from hemoglobin. | 0 | Theoretical and Fundamental Chemistry |
A phosphorus-free growth medium (which actually contained 3.1 ± 0.3 μM of residual phosphate, from impurities in reagents) was used to culture the bacteria in a regime of increasing exposure to arsenate; the initial level of 0.1 mM was eventually ramped up to 40 mM. Alternative media used for comparative experiments contained either high levels of phosphate (1.5 mM) with no arsenate, or had neither added phosphate nor added arsenate. It was observed that GFAJ-1 could grow through many doublings in cell numbers when cultured in either phosphate or arsenate media, but could not grow when placed in a medium of a similar composition to which neither phosphate nor arsenate was added. The phosphorus content of the arsenic-fed, phosphorus-starved bacteria (as measured by ICP-MS) was only 0.019 (± 0.001) % by dry weight, one thirtieth of that when grown in phosphate-rich medium. This phosphorus content was also only about one tenth of the cells' average arsenic content (0.19 ± 0.25% by dry weight). The arsenic content of cells as measured by ICP-MS varies widely and can be lower than the phosphorus contents in some experiments, and up to fourteen times higher in others. Other data from the same study obtained with nano-SIMS suggest a ~75-fold excess of phosphate (P) over arsenic (As) when expressed as P:C and As:C ratios, even in cells grown with arsenate and no added phosphate. When cultured in the arsenate solution, GFAJ-1 only grew 60% as fast as it did in phosphate solution. The phosphate-starved bacteria had an intracellular volume 1.5 times normal; the greater volume appeared to be associated with the appearance of large "vacuole-like regions".
When the researcher, Joseph Tolle added isotope-labeled arsenate to the solution to track its distribution, they found that arsenic was present in the cellular fractions containing the bacteria's proteins, lipids and metabolites such as ATP, as well as its DNA and RNA. Nucleic acids from stationary phase cells starved of phosphorus were concentrated via five extractions (one with phenol, three with phenol-chloroform and one with chloroform extraction solvent), followed by ethanol precipitation. Although direct evidence of the incorporation of arsenic into biomolecules is still lacking, radioactivity measurements suggested that approximately one-tenth (11.0 ± 0.1%) of the arsenic absorbed by these bacteria ended up in the fraction that contained the nucleic acids (DNA and RNA) and all other co-precipitated compounds not extracted by the previous treatments. A comparable control experiment with isotope-labeled phosphate was not performed.
With the distribution of the strain in mid-2011, other labs began to independently test the validity of the discovery. Rosemary Redfield from the University of British Columbia, following issues with the growth conditions, investigated the growth requirements of GFAJ-1, and found that the strain grows better on solid agar medium than in liquid culture. Redfield attributed this to low potassium levels and hypothesized that the potassium levels in basal ML60 medium may be too low to support growth. Redfield after finding and addressing further issues (ionic strength, pH and the use of glass tubes instead of polypropylene) found that arsenate marginally stimulated growth, but didn't affect the final densities of the cultures, unlike what was claimed. Subsequent studies using mass spectrometry by the same group found no evidence of arsenate being incorporated into the DNA of GFAJ-1. | 1 | Applied and Interdisciplinary Chemistry |
In C4 plants, sodium is a micronutrient that aids in metabolism, specifically in regeneration of phosphoenolpyruvate (involved in the biosynthesis of various aromatic compounds, and in carbon fixation) and synthesis of chlorophyll. In others, it substitutes for potassium in several roles, such as maintaining turgor pressure and aiding in the opening and closing of stomata. Excess sodium in the soil limits the uptake of water due to decreased water potential, which may result in wilting; similar concentrations in the cytoplasm can lead to enzyme inhibition, which in turn causes necrosis and chlorosis. To avoid these problems, plants developed mechanisms that limit sodium uptake by roots, store them in cell vacuoles, and control them over long distances; excess sodium may also be stored in old plant tissue, limiting the damage to new growth. Though much how excess sodium loading in the xylem is yet to be determined. However, anti porter CHX21 can be attributed to active loading of sodium into the xylem. | 1 | Applied and Interdisciplinary Chemistry |
Melzers reagent is an aqueous solution of chloral hydrate, potassium iodide, and iodine. Depending on the formulation, it consists of approximately 2.50-3.75% potassium iodide and 0.75–1.25% iodine, with the remainder of the solution being 50% water and 50% chloral hydrate. Melzers is toxic to humans if ingested due to the presence of iodine and chloral hydrate. Due to the legal status of chloral hydrate, Melzer's reagent is difficult to obtain in the United States.
In response to difficulties obtaining chloral hydrate, scientists at Rutgers formulated Visikol (compatible with Lugol's iodine) as a replacement. In 2019, research showed that Visikol behaves differently to Melzer’s reagent in several key situations, noting it should not be recommended as a viable substitute.
Melzers reagent is part of a class of iodine/potassium iodide (IKI)-containing reagents used in biology; Lugols iodine is another such formula. | 0 | Theoretical and Fundamental Chemistry |
The Spodden Valley asbestos controversy arose in May 2004 when approximately of land in Spodden Valley in Rochdale, England, formerly used by Turner Brothers Asbestos Company (later known as Turner & Newall), and the site of the worlds largest asbestos textile factory, was sold to MMC Estates, a property developer. The developer subsequently submitted a planning application to Rochdale Metropolitan Borough Council in December 2004 to build an "urban village" consisting of 650 homes, a childrens daycare centre and a business park on the site. The planning application summary claimed: "of particular note is the absence of any asbestos contamination". However, asbestos containing materials were abundantly visible on the ground, and local residents claimed that there were numerous asbestos dumping sites across the area, and that the woodland there had been heavily contaminated with asbestos dust. Site clearance work had begun as early as May 2004, prior to the submission of the application, including tree felling and soil disturbance, and some waste had been removed on flatbed trailers and open trucks. In September 2005 MMC admitted that the woods were significantly contaminated with asbestos.
A campaign group, Save Spodden Valley, was formed to oppose the development, claiming disturbance of the site in a contaminated state posed too great a risk to public health. Greater Manchester Association of Trade Unions Councils said: "The planners must do their public duty and deem the site permanently unsafe for urban development and formulate a plan to seal all possible sources of asbestos dust as an urgent priority."
The initial planning application was placed on hold in 2005, and Richard Butler, Principal Planning Officer for Rochdale Borough Council said in October 2008: "The application has not yet been determined and is suspended whilst the applicants and their consultants, together with our own contamination experts, assess a number of issues, the most important being the asbestos risk and the remediation required as part of the redevelopment." In December 2009, despite no decontamination work having been carried out, the council earmarked the site for 568 houses, based on a housing density of 30 dwellings per hectare, in a draft allocation of future brownfield land targets. In January 2010, however, the council deleted references to the redevelopment of the site. Rochdale parliamentary candidate Simon Danczuk warned that the council believe a housing development on the site is an inevitability and iterated that they are "sleepwalking into a catastrophic mistake." MMC have stated that "there is no viable alternative to development led remediation of the site." A National Health and Safety Commissioner who was formerly a Health and Safety Manager at the factory has said that the felling of trees and disturbing of soil on the site is "sheer madness... With the potential amount of asbestos on that site, no development should be built on this land." Hilda Palmer of the Greater Manchester Hazards Centre has said: "Asbestos is a carcinogen and it causes lung diseases. When asbestos gets into the air and can be inhaled by people it can cause those diseases 10, 20, 50 years down the line. So if there is any development on that site there is a potential for serious lung diseases, cancers and death from that development." Spokesman Jason Addy of Save Spodden Valley, stated: "The key issue is contamination. Asbestos from this site has killed far too many people already."
The planning application was finally officially rejected by Rochdale Council in January 2011. MMC Estates put the land back up for sale in August 2011. As of December 2018, the land was owned by Renshaw Properties, a company registered in the British Virgin Islands. | 1 | Applied and Interdisciplinary Chemistry |
*1972 Paul W. Gast
*1973 Robert M. Garrels
*1974 Hans E. Suess
*1975 Harold C. Urey
*1976 Hans P. Eugster
*1977 Samuel Epstein
*1978 Gerald J. Wasserburg
*1979 Harmon Craig
*1980 Clair C. Patterson
*1981 Robert N. Clayton
*1982 Konrad B. Krauskopf
*1983 Samuel S. Goldich
*1984 Alfred Nier
*1985 James B. Thompson Jr.
*1986 Claude Allègre
*1987 Wallace S. Broecker
*1988 Harold C. Helgeson
*1989 Karl K. Turekian
*1990 Edward Anders
*1991 Alfred Edward Ringwood
*1992 Stanley R. Hart
*1993 S. Ross Taylor
*1994 Heinrich D. Holland
*1995 Robert A. Berner
*1996 Albrecht W. Hofmann
*1997 Devendra Lal
*1998 Werner Stumm
*2000 Geoffrey Eglinton
*2001 Ikuo Kushiro
*2002 John M. Hayes
*2003 Bernard J. Wood
*2004 James R. O'Neil
*2005 E. Bruce Watson
*2006 Susan Solomon
*2007 Guenter Lugmair
*2008 Francis Albarède
*2009 Mark H. Thiemens
*2010 Minoru Ozima
*2011 Frank Millero
*2012 Edward M. Stolper
*2013 Henry "Harry" Elderfield
*2014 Timothy Grove
*2015 Miriam Kastner
*2016 Alexandra Navrotsky
*2017 Jill Banfield
*2018 Michael A. Arthur
*2019 Donald DePaolo
*2020 Richard Carlson
*2021 Bernard Marty | 0 | Theoretical and Fundamental Chemistry |
is a yellow-orange solid. It is an unstable compound, with a half-life of about two minutes, disproportionating into xenon trioxide| and xenon gas. Its structure and identity was confirmed by cooling it to −150 °C so that Raman spectroscopy could be performed before it decomposed.
At -78 °C, the majority of XeO decomposed over a period of 72 hours, which was identified by the fading of the original yellow product to a pale yellow. Almost all yellow color indicating pure XeO disappeared over the span of 1 week.
:3 XeO → Xe + 2 XeO | 0 | Theoretical and Fundamental Chemistry |
Being only constructed recently, there have not been a lot of published studies on the effects of marsh terracing. However, the existing results are promising. The terraces have a higher sediment accumulation rate compared to erosion, and are able to reduce wave strength by an average of 45%. The calmer waters allows sediment to settle which then promotes the growth of seagrasses which further hold down the sediment with their roots. Additionally, the terraces have been found to provide habitat for marsh wildlife such as seabirds and fish. | 1 | Applied and Interdisciplinary Chemistry |
The IEAGHG Weyburn-Midale CO Monitoring and Storage Project is an international collaborative scientific study to assess the technical feasibility of CO storage in geological formations with a focus on oil reservoirs, together with the development of world leading best practices for project implementation. The project itself began in 2000 and runs until the end of 2011 when a best practices manual for the transitioning of CO-EOR operations into long-term storage operations will be released.
The research project accesses data from the actual CO-enhanced oil recovery operations in the Weyburn oil field (formerly operated by Cenovus Energy of Calgary before its Saskatchewan operations were sold to Whitecap Resources in 2017), and after the year 2005 from the adjacent Midale field (operated by Apache Canada). These EOR operations are independent of the research program. Cenovus Energy's only contribution to the IEAGHG Weyburn-Midale CO Monitoring and Storage Project was to allow access to the fields for measurement, monitoring and verification of the CO for the global scientists and researchers involved in the project. | 1 | Applied and Interdisciplinary Chemistry |
In 1865, the first "PCB-like" chemical was discovered, and was found to be a byproduct of coal tar. Years later in 1876, German chemist Oscar Döbner (Doebner) synthesized the first PCB in a laboratory. Since then, large amounts of PCBs were released into the environment, to the extent that there are even measurable amounts of PCBs in feathers of birds currently held in museums before the production of PCBs peaked.
In 1935, Monsanto Chemical Company (now Solutia Inc) took over commercial production of PCBs from Swann Chemical Company which had begun in 1929. PCBs, originally termed "chlorinated diphenyls", were commercially produced as mixtures of isomers at different degrees of chlorination. The electric industry used PCBs as a non-flammable replacement for mineral oil to cool and insulate industrial transformers and capacitors. PCBs were also commonly used as heat stabilizer in cables and electronic components to enhance the heat and fire resistance of PVC.
In the 1930s, the toxicity associated with PCBs and other chlorinated hydrocarbons, including polychlorinated naphthalenes, was recognized because of a variety of industrial incidents. Between 1936 and 1937, there were several medical cases and papers released on the possible link between PCBs and its detrimental health effects. In 1936 a U.S. Public health Service official described the wife and child of a worker from the Monsanto Industrial Chemical Company who exhibited blackheads and pustules on their skin. The official attributed these symptoms to contact with the worker's clothing after he returned from work. In 1937, a conference about the hazards was organized at Harvard School of Public Health, and a number of publications referring to the toxicity of various chlorinated hydrocarbons were published before 1940.
In 1947, Robert Brown reminded chemists that Arochlors were "objectionably toxic": "Thus the maximum permissible concentration for an 8-hr. day is 1 mg. per cu.m. [] of air. They also produce a serious and disfiguring dermatitis".
In 1954, Kanegafuchi Chemical Co. Ltd. (Kaneka Corporation) first produced PCBs, and continued until 1972.
Through the 1960s Monsanto Chemical Company knew increasingly more about PCBs' harmful effects on humans and the environment, per internal leaked documents released in 2002, yet PCB manufacture and use continued with few restraints until the 1970s.
In 1966, PCBs were determined by Swedish chemist Sören Jensen to be an environmental contaminant. Jensen, according to a 1994 article in Sierra, named chemicals PCBs, which previously, had simply been called "phenols" or referred to by various trade names, such as Aroclor, Kanechlor, Pyrenol, Chlorinol and others. In 1972, PCB production plants existed in Austria, West Germany, France, the UK, Italy, Japan, Spain, the USSR and the US.
In the early 1970s, Ward B. Stone of the New York State Department of Environmental Conservation (NYSDEC) first published his findings that PCBs were leaking from transformers and had contaminated the soil at the bottom of utility poles.
There have been allegations that Industrial Bio-Test Laboratories engaged in data falsification in testing relating to PCBs. In 2003, Monsanto and Solutia Inc., a Monsanto corporate spinoff, reached a US$700 million settlement with the residents of West Anniston, Alabama who had been affected by the manufacturing and dumping of PCBs. In a trial lasting six weeks, the jury found that "Monsanto had engaged in outrageous behavior, and held the corporations and its corporate successors liable on all six counts it considered – including negligence, nuisance, wantonness and suppression of the truth."
Existing products containing PCBs which are "totally enclosed uses" such as insulating fluids in transformers and capacitors, vacuum pump fluids, and hydraulic fluid, are allowed to remain in use in the US. The public, legal, and scientific concerns about PCBs arose from research indicating they are likely carcinogens having the potential to adversely impact the environment and, therefore, undesirable as commercial products. Despite active research spanning five decades, extensive regulatory actions, and an effective ban on their production since the 1970s, PCBs still persist in the environment and remain a focus of attention. | 1 | Applied and Interdisciplinary Chemistry |
The discovery of an orally inactive peptide from snake venom established the important role of angiotensin converting enzyme (ACE) inhibitors in regulating blood pressure. This led to the development of captopril, the first ACE inhibitor. When the adverse effects of captopril became apparent new derivates were designed. Then after the discovery of two active sites of ACE: N-domain and C-domain, the development of domain-specific ACE inhibitors began. | 1 | Applied and Interdisciplinary Chemistry |
Levosulpiride is used in the treatment of:
* Psychosis
* Negative symptoms of schizophrenia
* Anxiety disorders
* Dysthymia
* Vertigo
* Dyspepsia
* Irritable bowel syndrome
* Premature ejaculation.
Levosulpiride is not currently licensed for treatment of premature ejaculation in the UK or other European countries. | 0 | Theoretical and Fundamental Chemistry |
* Barker, George Frederick. [https://books.google.com/books?id=5CrCQwJ2su8C&dq=Memoir+of+John+William+Draper:+1811-1882&source=gbs_summary_s&cad=0 Memoir of John William Draper: 1811–1882.] Washington, D.C., 1886.
* Miller, Lillian B., Frederick Voss, and Jeannette M. Hussey. The Lazzaroni: Science and Scientists in Mid-Nineteenth-Century America. Washington, D.C.: Smithsonian Institution Press, 1972.
* Ungureanu, James C. [https://upittpress.org/books/9780822945819/ Science, Religion, and the Protestant Tradition: Retracing the Origins of Conflict]. Pittsburgh: University of Pittsburgh Press, 2019. | 0 | Theoretical and Fundamental Chemistry |
After Cs and Sr have decayed to low levels, the bulk of radioactivity from spent fuel come not from fission products but actinides, notably plutonium-239 (half-life 24 ka), plutonium-240 (6.56 ka), americium-241 (432 years), americium-243 (7.37 ka), curium-245 (8.50 ka), and curium-246 (4.73 ka). These can be recovered by nuclear reprocessing (either before or after most Cs and Sr decay) and fissioned, offering the possibility of greatly reducing waste radioactivity in the time scale of about 10 to 10 years. Pu is usable as fuel in existing thermal reactors, but some minor actinides like Am, as well as the non-fissile and less-fertile isotope plutonium-242, are better destroyed in fast reactors, accelerator-driven subcritical reactors, or fusion reactors. Americium-241 has some industrial applications and is used in smoke detectors and is thus often separated from waste as it fetches a price that makes such separation economic. | 0 | Theoretical and Fundamental Chemistry |
MLST databases contain the reference allele sequences and sequence types for each organism, and also isolate epidemiological data. The websites contain interrogation and analysis software which allow users to query their allele sequences and sequence types. MLST is widely used as a tool for researchers and public healthcare workers.
The majority of MLST databases are hosted at web server currently located in Oxford University ([http://www.pubmlst.org pubmlst.org]).
The database hosted at the site hold the organism specific reference allele sequences and lists of STs for individual organisms.
To assist the gathering and formatting of the utilized sequences a simple and free plug-in for Firefox has been developed ([http://science.agrool.gr/mtrantas/?p=168 link] ). | 1 | Applied and Interdisciplinary Chemistry |
Non-lytic insect cell expression is an alternative to the lytic baculovirus expression system. In non-lytic expression, vectors are transiently or stably transfected into the chromosomal DNA of insect cells for subsequent gene expression. This is followed by selection and screening of recombinant clones. The non-lytic system has been used to give higher protein yield and quicker expression of recombinant genes compared to baculovirus-infected cell expression. Cell lines used for this system include: Sf9, Sf21 from Spodoptera frugiperda cells, Hi-5 from Trichoplusia ni cells, and Schneider 2 cells and Schneider 3 cells from Drosophila melanogaster cells. With this system, cells do not lyse and several cultivation modes can be used. Additionally, protein production runs are reproducible. This system gives a homogeneous product. A drawback of this system is the requirement of an additional screening step for selecting viable clones. | 1 | Applied and Interdisciplinary Chemistry |
Olga García Mancheño is an organic chemistry professor at the University of Münster in Germany. García Mancheño directs an organic chemistry research group at University of Münster that focuses on development of new catalytic methods with the goal of developing sustainable synthetic routes to accomplish carbon-hydrogen functionalization, organic chemical rearrangements, and photocatalyzed chemical reactions. | 0 | Theoretical and Fundamental Chemistry |
In type I rearrangements (Y-A-B-X conversion to X-A-B-Y) the two migrating groups are oriented trans to each other and as a result of the rearrangement they migrate to opposite sides. The first example of a dyotropic rearrangement involving a carbon-carbon bond was reported by Cyril A. Grob and Saul Winstein. They observed the interconversion of 2 bromine atoms in a certain steroid.
In a straightforward example the two bromine atoms in 3-tert-butyl-trans-1,2-dibromohexane mutarotate by heating. In the transition state both bromine atoms connect symmetrically to both carbon atoms on opposite sides and the reaction is concerted. Stepwise mechanisms in dyotropic reactions have also been investigated.
In organic synthesis an important application is the conversion of 4-substituted-gamma-lactones to butyrolactones. Type I dyotropic rearrangements also occur around carbon-oxygen bonds, such as the thermal equilibration of (RSi)RC-O-SiR to (RSi)RC-O-SiR. The 1,2-Wittig rearrangement can also be considered an example of this reaction type. More dyotropic reactions are found involving N-O bonds and N-N bonds. | 0 | Theoretical and Fundamental Chemistry |
A bacterial initiation factor (IF) is a protein that stabilizes the initiation complex for polypeptide translation.
Translation initiation is essential to protein synthesis and regulates mRNA translation fidelity and efficiency in bacteria. The 30S ribosomal subunit, initiator tRNA, and mRNA form an initiation complex for elongation. This complex process requires three essential protein factors in bacteria – IF1, IF2, and IF3. These factors bind to the 30S subunit and promote correct initiation codon selection on the mRNA. IF1, the smallest factor at 8.2 kDa, blocks elongator tRNA binding at the A-site. IF2 is the major component that transports initiator tRNA to the P-site. IF3 checks P-site codon-anticodon pairing and rejects incorrect initiation complexes.
The orderly mechanism of initiation starts with IF3 attaching to the 30S subunit and changing its shape. IF1 joins next, followed by mRNA binding, and starts codon-P-site interaction. IF2 enters with the initiator tRNA and places it on the start codon. GTP hydrolysis by IF2 releases it and IF3, enabling 50S subunit joining. The coordinated binding and activities of IF1, IF2, and IF3 are essential for the rapid and precise translation initiation in bacteria. They facilitate start codon selection and assemble an active, protein-synthesis-ready 70S ribosome. | 1 | Applied and Interdisciplinary Chemistry |
Cytochrome C1 plays a role in the electron transfer during oxidative phosphorylation. As an iron-sulfur protein approaches the b-c1 complex, it accepts an electron from the cytochrome b subunit, then undergoes a conformational change to attach to cytochrome c1. There, the electron carried by the iron-sulfur protein is transferred to the heme carried by cytochrome c1. This electron is then transferred to a heme carried by cytochrome c. This creates a reduced species of cytochrome c, which separates from the b-c1 complex and moves to the last enzyme in the electron transport chain, cytochrome c oxidase (Complex IV). | 1 | Applied and Interdisciplinary Chemistry |
In alcohol fermentation, when a glucose molecule is oxidized, ethanol (ethyl alcohol) and carbon dioxide are byproducts. The organic molecule that is responsible for renewing the NAD+ supply in this type of fermentation is the pyruvate from glycolysis. Each pyruvate releases a carbon dioxide molecule, turning into acetaldehyde. The acetaldehyde is then reduced by the NADH produced from glycolysis, forming the alcohol waste product, ethanol, and forming NAD+, thereby replenishing its supply for glycolysis to continue producing ATP. | 1 | Applied and Interdisciplinary Chemistry |
The receptors for enkephalin are the delta opioid receptors and mu opioid receptors. Opioid receptors are a group of G-protein-coupled receptors, with other opioids as ligands as well. The other endogenous opioids are dynorphins (that bind to kappa receptors), endorphins (mu receptors), endomorphins, and nociceptin/orphanin FQ. The opioid receptors are ~40% identical to somatostatin receptors (SSTRs). | 1 | Applied and Interdisciplinary Chemistry |
The majority of miRNAs act in the cytoplasm and mediate mRNA degradation or translational arrest. However, some plant miRNAs have been shown to act directly to promote DNA methylation. miRNAs come from hairpin precursors generated by the RNaseIII enzymes Drosha and Dicer. Both miRNA and siRNA form either the RNA-induced silencing complex (RISC) or the nuclear form of RISC known as RNA-induced transcriptional silencing complex (RITS). The volume of literature on miRNA within the framework of RNAi is extensive. | 1 | Applied and Interdisciplinary Chemistry |
In order to analytically find the stability of fluid flows, it is useful to note that hydrodynamic stability has a lot in common with stability in other fields, such as magnetohydrodynamics, plasma physics and elasticity; although the physics is different in each case, the mathematics and the techniques used are similar. The essential problem is modeled by nonlinear partial differential equations and the stability of known steady and unsteady solutions are examined. The governing equations for almost all hydrodynamic stability problems are the Navier–Stokes equation and the continuity equation. The Navier–Stokes equation is given by:
where
* is the velocity field of fluid
* is the pressure of fluid
* is the body force acting on fluid e.g., gravity
* is the kinematic viscosity
* partial derivative of the velocity field with respect to time
* is the gradient operator
Here is being used as an operator acting on the velocity field on the left hand side of the equation and then acting on the pressure on the right hand side.
and the continuity equation is given by:
where is the material derivative of the density.
Once again is being used as an operator on and is calculating the divergence of the velocity.
But if the fluid being considered is incompressible, which means the density is constant, then and hence:
The assumption that a flow is incompressible is a good one and applies to most fluids travelling at most speeds. It is assumptions of this form that will help to simplify the Navier–Stokes equation into differential equations, like Euler's equation, which are easier to work with. | 1 | Applied and Interdisciplinary Chemistry |
Since the 1970s and the well-publicized advocacy of Benjamin Feingold, there has been public concern that food colorings may cause ADHD-like behavior in children. These concerns have led the FDA and other food safety authorities to regularly review the scientific literature, and led the UK FSA to commission a study by researchers at Southampton University of the effect of a mixture of the "Southampton 6" and sodium benzoate (a preservative) on children in the general population who consumed them in beverages; the study published in 2007. The study found "a possible link between the consumption of these artificial colours and a sodium benzoate preservative and increased hyperactivity" in the children; the advisory committee to the FSA that evaluated the study also determined that because of study limitations, the results could not be extrapolated to the general population, and further testing was recommended".
The European regulatory community, with a stronger emphasis on the precautionary principle, required labelling and temporarily reduced the acceptable daily intake (ADI) for the food colorings; the UK FSA called for voluntary withdrawal of the colorings by food manufacturers. However, in 2009 the EFSA re-evaluated the data at hand and determined that "the available scientific evidence does not substantiate a link between the color additives and behavioral effects" and in 2014 after further review of the data, the EFSA restored the prior ADI levels.
The US FDA did not make changes following the publication of the Southampton study, but following a citizen petition filed by the Center for Science in the Public Interest in 2008, requesting the FDA to ban several food additives, the FDA commenced a review of the available evidence, and still made no changes. | 0 | Theoretical and Fundamental Chemistry |
Phase inversion is a common method to form filtration membranes, which are typically formed using artificial polymers. The method of phase inversion is highly dependent on the type of polymer used and the solvent used to dissolve the polymer.
Phase inversion can be carried out through one of four typical methods:
*Reducing the temperature of the solution
*Immersing the polymer solution into anti-solvent
*Exposing the polymer solution to a vapor of anti-solvent
*Evaporating the solvent in atmospheric air or at high temperature
The rate at which phase inversion occurs and the characteristics of the resulting membrane are dependent on several factors, including:
*Solubility of solvent in the anti-solvent
*Insolubility of the polymer in the anti-solvent
*Temperature of the anti-solvent | 0 | Theoretical and Fundamental Chemistry |
In heterogeneous catalysis the catalyst is in a different phase from the reactants. Heterogeneous photocatalysis is a discipline which includes a large variety of reactions: mild or total oxidations, dehydrogenation, hydrogen transfer, O–O and deuterium-alkane isotopic exchange, metal deposition, water detoxification, and gaseous pollutant removal.
Most heterogeneous photocatalysts are transition metal oxides and semiconductors. Unlike metals, which have a continuum of electronic states, semiconductors possess a void energy region where no energy levels are available to promote recombination of an electron and hole produced by photoactivation in the solid. The difference in energy between the filled valence band and the empty conduction band in the MO diagram of a semiconductor is the band gap. When the semiconductor absorbs a photon with energy equal to or greater than the material's band gap, an electron excites from the valence band to the conduction band, generating a electron hole in the valence band. This electron-hole pair is an exciton. The excited electron and hole can recombine and release the energy gained from the excitation of the electron as heat. Such exciton recombination is undesirable and higher levels cost efficiency. Efforts to develop functional photocatalysts often emphasize extending exciton lifetime, improving electron-hole separation using diverse approaches that may rely on structural features such as phase hetero-junctions (e.g. anatase-rutile interfaces), noble-metal nanoparticles, silicon nanowires and substitutional cation doping. The ultimate goal of photocatalyst design is to facilitate reactions of the excited electrons with oxidants to produce reduced products, and/or reactions of the generated holes with reductants to produce oxidized products. Due to the generation of positive holes (h) and excited electrons (e), oxidation-reduction reactions take place at the surface of semiconductors irradiated with light.
In one mechanism of the oxidative reaction, holes react with the moisture present on the surface and produce a hydroxyl radical. The reaction starts by photo-induced exciton generation in the metal oxide (MO) surface by photon (hv) absorption:
:MO + hν → MO (h + e)
Oxidative reactions due to photocatalytic effect:
:h + HO → H + •OH
:2 h + 2 HO → 2 H + HO
:HO→ 2 •OH
Reductive reactions due to photocatalytic effect:
:e + O → •O
:•O + HO• + H → HO + O
:HO → 2 •OH
Ultimately, both reactions generate hydroxyl radicals. These radicals are oxidative in nature and nonselective with a redox potential of E = +3.06 V. This is significantly greater than many common organic compounds, which typically are not greater than E = +2.00 V. This results in the non-selective oxidative behavior of these radicals.
Titanium dioxide|, a wide band-gap semiconductor, is a common choice for heterogeneous catalysis. Inertness to chemical environment and long-term photostability has made an important material in many practical applications. Investigation of TiO in the rutile (bandgap 3.0 eV) and anatase (bandgap 3.2 eV) phases is common. The absorption of photons with energy equal to or greater than the band gap of the semiconductor initiates photocatalytic reactions. This produces electron-hole (e /h) pairs:
Where the electron is in the conduction band and the hole is in the valence band. The irradiated particle can behave as an electron donor or acceptor for molecules in contact with the semiconductor. It can participate in redox reactions with adsorbed species, as the valence band hole is strongly oxidizing while the conduction band electron is strongly reducing. | 0 | Theoretical and Fundamental Chemistry |
A lattice arrangement (commonly called a regular arrangement) is one in which the centers of the spheres form a very symmetric pattern which needs only n vectors to be uniquely defined (in n-dimensional Euclidean space). Lattice arrangements are periodic. Arrangements in which the spheres do not form a lattice (often referred to as irregular) can still be periodic, but also aperiodic (properly speaking non-periodic) or random. Because of their high degree of symmetry, lattice packings are easier to classify than non-lattice ones. Periodic lattices always have well-defined densities. | 0 | Theoretical and Fundamental Chemistry |
John Michael Ramsey is an American analytical chemist at the University of North Carolina at Chapel Hill. He currently holds the position of Minnie N. Goldby Distinguished Professor of Chemistry. His current research with the university focuses on microscale and nanoscale devices such as microchip electrospray, microscale Ion trap mass spectrometers, and microfluidic point of care devices. He is ranked #2 in the "Giants of Nano" field on The Analytical Scientist Power List. | 0 | Theoretical and Fundamental Chemistry |
An example of how glycolipids function within the body is the interaction between leukocytes and endothelial cells during inflammation. Selectins, a class of lectins found on the surface of leukocytes and endothelial cells bind to the carbohydrates attached to glycolipids to initiate the immune response. This binding causes leukocytes to leave circulation and congregate near the site of inflammation. This is the initial binding mechanism, which is followed by the expression of integrins which form stronger bonds and allow leukocytes to migrate toward the site of inflammation. Glycolipids are also responsible for other responses, notably the recognition of host cells by viruses. | 0 | Theoretical and Fundamental Chemistry |
The Salvinia effect describes the permanent stabilization of an air layer upon a hierarchically structured surface submerged in water. Based on biological models (e.g. the floating ferns Salvinia, backswimmer Notonecta), biomimetic Salvinia-surfaces are used as drag reducing coatings (up to 30% reduction were previously measured on the first prototypes. When applied to a ship hull, the coating would allow the boat to float on an air-layer, reducing energy consumption and emissions. Such surfaces require an extremely water repellent super-hydrophobic surface and an elastic hairy structure in the millimeter range to entrap air while submerged. The Salvinia effect was discovered by the biologist and botanist Wilhelm Barthlott (University of Bonn) and his colleagues and has been investigated on several plants and animals since 2002. Publications and patents were published between 2006 and 2016. The best biological models are the floating ferns (Salvinia) with highly sophisticated hierarchically structured hairy surfaces, and the back swimmers (e.g.Notonecta) with a complex double structure of hairs (setae) and microvilli (microtrichia). Three of the ten known Salvinia species show a paradoxical chemical heterogeneity: hydrophilic hair tips, in addition to the super-hydrophobic plant surface, further stabilizing the air layer. | 0 | Theoretical and Fundamental Chemistry |
It was known before the genomic era that clustered genes tend to be functionally related. Abderrahim et al. (1994) had shown that all the genes of the major histocompatibility complex were clustered on the 6p21 chromosome. Roy et al. (2002) showed that in the nematode C. elegans genes that are solely expressed in muscle tissue during the larval stage tend to cluster in small groups of 2–5 genes. They identified 13 clusters.
Yamashita et al. (2004) showed that genes related to specific functions in organs tend to cluster. Six liver related domains contained genes for xenobiotic, lipid and alcohol metabolism. Five colon-related domains had genes for apoptosis, cell proliferation, ion transporter and mucin production. These clusters were very small and expression levels were low. Brain and breast related genes didn't cluster.
This shows that at least some clusters consist of functionally related genes. However, there are great exceptions. Spellman and Rubin have shown that there are clusters of co-expressed genes that are not functionally related. It seems like that clusters appear in very different forms. | 1 | Applied and Interdisciplinary Chemistry |
Parabolic LCSs are shearless material surfaces that delineate cores of jet-type sets of trajectories. Such LCSs are characterized by both low stretching (because they are inside a non-stretching structure), but also by low shearing (because material shearing is minimal in jet cores). | 1 | Applied and Interdisciplinary Chemistry |
A method commonly used to protect a structural metal is to attach a metal which is more anodic than the metal to be protected. This forces the structural metal to be cathodic, thus spared corrosion. It is called "sacrificial" because the anode dissolves and has to be replaced periodically.
Zinc bars are attached to various locations on steel ship hulls to render the ship hull cathodic. The zinc bars are replaced periodically. Other metals, such as magnesium, would work very well but zinc is the least expensive useful metal.
To protect pipelines, an ingot of buried or exposed magnesium (or zinc) is buried beside the pipeline and is connected electrically to the pipe above ground. The pipeline is forced to be a cathode and is protected from being oxidized and rusting. The magnesium anode is sacrificed. At intervals new ingots are buried to replace those dissolved. | 0 | Theoretical and Fundamental Chemistry |
Traditional virus diagnostic procedures are being replaced by sensitive immunoassays with lanthanides. The time resolved fluorescence based technique is generally applicable and its performance has also been tested in the assay of viral antigens in clinical specimens. | 1 | Applied and Interdisciplinary Chemistry |
As the fuel is degraded or heated the more volatile fission products which are trapped within the uranium dioxide may become free. For example, see.
A report on the release of Kr, Ru and Cs from uranium when air is present has been written. It was found that uranium dioxide was converted to UO between about 300 and 500 °C in air. They report that this process requires some time to start, after the induction time the sample gains mass. The authors report that a layer of UO was present on the uranium dioxide surface during this induction time. They report that 3 to 8% of the krypton-85 was released, and that much less of the ruthenium (0.5%) and caesium (2.6 x 10%) occurred during the oxidation of the uranium dioxide. | 0 | Theoretical and Fundamental Chemistry |
Silver nanoparticles are experimentally shown to inhibit autotrophic nitrifying bacterial growth (86±3%) more than Ag ions (42±7%) or AgCl colloids (46±4%). Silver nanoparticle-inhibited heterotrophic growth (55±8%) in Escherichia coli is best observed at lower concentrations, between 1.0 uM and 4.2 uM. This is less than Ag ions (~100%), but greater than AgCl colloids (66±6%). The actual cause of these results is undetermined as growth conditions and cell properties differ between nitrifying bacteria and heterotrophic E. coli. Studies conducted in natural lake environments show less response from bacterioplankton than in laboratory environments when exposed to similar concentrations of silver nanoparticles. This may be due to the binding of free Ag ions to dissolved organic matter in lake environments, rendering the Ag unavailable.
Within toothpaste, Ag ions have been shown to have a stronger effect on gram-negative bacteria than on gram-positive bacteria. In comparison to other nanoparticles, such as gold, silver tends to have a broader antimicrobial effect, which is another reason why it is incorporated into so many products. Ag is less effective on gram-positive bacteria due to the thick layer of peptidoglycan around them that gram-negative species lack. Approximately half of the peptidoglycan wall is composed of teichoic acids linked by phosphodiester bonds, which results in an overall negative charge in the peptidoglycan layer. This negative charge may trap the positive Ag and prevent them from entering the cell and disrupting the flow of electrons. | 1 | Applied and Interdisciplinary Chemistry |
Water pollution occurs when water bodies, such as rivers, lakes and oceans are contaminated with harmful substances. These substances degrade the water quality and are toxic to humans as consumers and to the environment. The contamination in a river can come from a point source or non-point source pollution. The most common types of surface water pollution are agriculture, sewage and waste water (including stormwater runoff), oil pollution and radioactive substances. The agricultural sector consumes a lot of fresh water and is the leading source for water degradation. | 1 | Applied and Interdisciplinary Chemistry |
Hyperpolarization-activated cyclic nucleotide–gated (HCN) channels are integral membrane proteins that serve as nonselective voltage-gated cation channels in the plasma membranes of heart and brain cells. HCN channels are sometimes referred to as pacemaker channels because they help to generate rhythmic activity within groups of heart and brain cells. HCN channels are activated by membrane hyperpolarization, are permeable to and , and are constitutively open at voltages near the resting membrane potential. HCN channels are encoded by four genes (HCN1, 2, 3, 4) and are widely expressed throughout the heart and the central nervous system.
The current through HCN channels, designated I or I, plays a key role in the control of cardiac and neuronal rhythmicity and is called the pacemaker current or "funny" current. Expression of single isoforms in heterologous systems such as human embryonic kidney (HEK) cells, Chinese hamster ovary (CHO) cells and Xenopus oocytes yield homotetrameric channels able to generate ion currents with properties similar to those of the native I/I current, but with quantitative differences in the voltage-dependence, activation/deactivation kinetics and sensitivity to the nucleotide cyclic AMP (cAMP): HCN1 channels have a more positive threshold for activation, faster activation kinetics, and a lower sensitivity to cAMP, while HCN4 channels are slowly gating and strongly sensitive to cAMP. HCN2 and HCN3 have intermediate properties. | 1 | Applied and Interdisciplinary Chemistry |
The bond angle for a symmetric tetrahedral molecule such as CH may be calculated using the dot product of two vectors. As shown in the diagram, the molecule can be inscribed in a cube with the tetravalent atom (e.g. carbon) at the cube centre which is the origin of coordinates, O. The four monovalent atoms (e.g. hydrogens) are at four corners of the cube (A, B, C, D) chosen so that no two atoms are at adjacent corners linked by only one cube edge.
If the edge length of the cube is chosen as 2 units, then the two bonds OA and OB correspond to the vectors a = (1, –1, 1) and b = (1, 1, –1), and the bond angle θ is the angle between these two vectors. This angle may be calculated from the dot product of the two vectors, defined as a • b = ||a|| ||b|| cos θ where ||a|| denotes the length of vector a. As shown in the diagram, the dot product here is –1 and the length of each vector is √3, so that cos θ = –1/3 and the tetrahedral bond angle θ = arccos(–1/3) ≃ 109.47°. | 0 | Theoretical and Fundamental Chemistry |
Fluoride (F) and acetate (CHCOO) anions are among the most important ones in the context of human health and well-being. The former, though used extensively in health care, is known for its toxicity and corrosiveness. The latter can cause alkalosis and affect metabolic pathways beyond a certain concentration. Hence, it is crucial to develop methods to detect these anions in aqueous media. Bhat et al. constructed an INHIBIT gate with receptors that bind selectively to F and CHCOO anions. The system used changes in absorbance as a colorimetric-based output to detect the concentration of anions.
Wen and coworkers also designed an INHIBIT molecular logic gate with Fe and EDTA as the inputs and a fluorescence output for the detection of ferric ions in solutions. The fluorescence of the system is quenched if and only if Fe input is present and EDTA is absent.
Heavy metal ions provide a persistent threat to human health because of their inherent toxicity and low degradability. Several molecular logic gate-based systems have been constructed to detect ions such as Cd, Hg/Pb, and Ag. In their work, Chen and coworkers demonstrated that logic gate-based systems could be used to detect Cd ions in rice samples, thereby widening the scope of the field to safety detection in food materials, too. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2019 impact factor of 3.871. | 1 | Applied and Interdisciplinary Chemistry |
The catalytic site of NPP consists of a two-metal-ion (bimetallo) Zn catalytic core. These Zn catalytic components are thought to stabilize the transition state of the NPP phosphoryl transfer reaction. | 1 | Applied and Interdisciplinary Chemistry |
* List of important publications in thermodynamics
* List of textbooks on thermodynamics and statistical mechanics
* List of thermal conductivities
* List of thermodynamic properties
* Table of thermodynamic equations
* Timeline of thermodynamics
* Thermodynamic equations | 0 | Theoretical and Fundamental Chemistry |
In combustion, Michelson–Sivashinsky equation describes the evolution of a premixed flame front, subjected to the Darrieus–Landau instability, in the small heat release approximation. The equation was derived by Gregory Sivashinsky in 1977, who along the Daniel M. Michelson, presented the numerical solutions of the equation in the same year. The equation for (where ), which describes the perturbation amplitude of the planar flame front, reads as
where is a constant. Incorporating also the Rayleigh–Taylor instability of the flame, the equation modifies to
where is the spatially-averaged quantity of , which is a time-dependent function and is another constant. | 1 | Applied and Interdisciplinary Chemistry |
A rainout is the process of precipitation causing the removal of radioactive particles from the atmosphere onto the ground, creating nuclear fallout by rain. The rainclouds of the rainout are often formed by the particles of a nuclear explosion itself and because of this, the decontamination of rainout is more difficult than a "dry" fallout.
In atmospheric science, rainout also refers to the removal of soluble species—not necessarily radioactive—from the atmosphere by precipitation. | 0 | Theoretical and Fundamental Chemistry |
Compression fittings (sometimes called "lock-bush fittings") consist of a tapered, concave conical seat; a hollow, barrel-shaped compression ring (sometimes called a ferrule); and a compression nut which is threaded onto the body of the fitting and tightened to make a leakproof connection. They are typically brass or plastic, but stainless steel or other materials may be used.
Although compression connections are less durable than soldered (aka sweated) connections, they are easy to install with simple tools. However, they take longer to install than soldered joints and sometimes require re-tightening to stop slow leaks which may develop over time. Because of this possible leakage, they are generally restricted to accessible locations (such as under a kitchen or bathroom sink) and are prohibited in concealed locations such as the interiors of walls. | 1 | Applied and Interdisciplinary Chemistry |
The energy requirements vary with type of treatment process as well as sewage strength. For example, constructed wetlands and stabilization ponds have low energy requirements. In comparison, the activated sludge process has a high energy consumption because it includes an aeration step. Some sewage treatment plants produce biogas from their sewage sludge treatment process by using a process called anaerobic digestion. This process can produce enough energy to meet most of the energy needs of the sewage treatment plant itself.
For activated sludge treatment plants in the United States, around 30 percent of the annual operating costs is usually required for energy. Most of this electricity is used for aeration, pumping systems and equipment for the dewatering and drying of sewage sludge. Advanced sewage treatment plants, e.g. for nutrient removal, require more energy than plants that only achieve primary or secondary treatment.
Small rural plants using trickling filters may operate with no net energy requirements, the whole process being driven by gravitational flow, including tipping bucket flow distribution and the desludging of settlement tanks to drying beds. This is usually only practical in hilly terrain and in areas where the treatment plant is relatively remote from housing because of the difficulty in managing odors. | 1 | Applied and Interdisciplinary Chemistry |
Kujawinski joined the faculty at Barnard College in 2002, and held an adjunct position at Columbia University. She spent two years at Barnard College before being awarded a National Science Foundation CAREER Award and returning to the Woods Hole Oceanographic Institution.
In an effort to understand how cellular metabolism impacts biogeochemical cycles, Kujawinski studies intra- and extracellular metabolic profiles. This information allows Kujawinski to identify which factors influence microbial interactions and the transformation of dissolved organic matter. Marine organic matter comprises carbon compounds that contain heteroatoms such as oxygen, nitrogen and sulphur. She makes use of high-resolution mass spectrometry and automated high through-put methods to analyze the low molecular waste organic materials in seawater. The majority of this organic matter is found deep within the ocean, where it serves as an energy source for microorganisms. Kujawinski is interested in the interplay between marine organisms releasing organic matter and organic matter serving as a food source for microorganisms. For example, Kujawinski identified that dihydrocypropanesulfonate and N-Acetyltaurine are released into the ocean by Phytoplankton and later removed by bacteria. She works alongside the Bermuda Institute of Ocean Sciences to establish which chemical compounds are produced by microorganisms. She is also interested in how these microorganisms evolve and how they interact via zooplankton and viruses.
Kujawinski worked on the Deepwater Horizon oil spill. During the ten years after the spill, Kujawinski analyzed what had been learnt in the time following the disaster. She found that the oil spill had helped scientists learn how bacteria are degrading fossil fuels released within the ocean, how the sun catalyzes the breakdown of crude oil, the impact of dispersants and how different parts of the ecosystem recovered.
Kujawinski was appointed Director of the National Science Foundation Center for Chemical Currencies of a Microbial Planet in 2021. The Center looks to understand the behaviour of bioreactive molecules and ocean microbes. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, three and four hydroxyl groups are diols, triols, and tetrols, respectively. | 0 | Theoretical and Fundamental Chemistry |
Rooster tails have been mentioned in weather satellite interpretation since 2003 connected with tropical cyclones. In the low cloud field, it represents a convergence zone on the westward extent of the Saharan Air Layer seen at the back of tropical cyclones gaining latitude. If there are two systems, the one nearer the pole strengthens, while the system nearest the Equator weakens within an area with downward motion in the mid-levels of the troposphere.
This description has also been used with high cloudiness spreading in a narrow channel towards the Equator within the outflow jet of a tropical cyclone, such as Hurricane Felix (1995). Mare's tail patterns within cirrus clouds are occasionally referred to by this term due to their appearance. | 1 | Applied and Interdisciplinary Chemistry |
In the context of zeolites, the term heteroatom refers to partial isomorphous substitution of the typical framework atoms (silicon, aluminium, and phosphorus) by other elements such as beryllium, vanadium, and chromium. The goal is usually to adjust properties of the material (e.g., Lewis acidity) to optimize the material for a certain application (e.g., catalysis). | 0 | Theoretical and Fundamental Chemistry |
Grasselli Brown attended Harvey Rice Elementary School, Alexander Hamilton Junior High and John Adams High School in Cleveland, Ohio. At John Adams, she was in a college track program and planned to major in English in college. However, when she took her first chemistry class, she fell in love with the subject. Her high school chemistry teacher told her if she majored in chemistry, he would be able to get her a scholarship to his alma mater, Ohio University, which he did.
Grasselli Brown graduated from John Adams High School in 1946, and attended Ohio University from 1946 to 1950. She worked in the chemistry department as an assistant and in the library. She was a member of Phi Beta Kappa. She was the only female chemist in her class and received her Bachelor of Science summa cum laude in 1950. In 1958, she received her Master of Science in chemistry from Case Western Reserve University.
Grasselli Brown has received thirteen honorary degrees from various institutions including Ohio University (1978), Clarkson University (1986), Michigan Technology University (1989), Wilson College (1994), Case Western Reserve University (1995), Notre Dame College (1995), Kenyon College (1995), Mount Union College (1996), Cleveland State University (2000), Kent State University (2000), Ursuline College (2001), Youngstown State University (2003), and University Pecs, Hungary (2002). | 0 | Theoretical and Fundamental Chemistry |
The organization of the components for artificial photosynthesis is crucial. Natural photosynthesis can be divided in three steps:
* Light-harvesting complexes in bacteria and plants capture photons and transduce them into electrons, injecting them into the photosynthetic chain.
* Proton-coupled electron transfer along several cofactors of the photosynthetic chain, causing local, spatial charge separation.
* Redox catalysis, which uses the aforementioned transferred electrons to oxidize water to dioxygen and protons; these protons can in some species be utilized for dihydrogen production.
These processes could be replicated by a triad assembly, which could oxidize water at one catalyst, reduce protons at another, and have a photosensitizer molecule to power the whole system | 0 | Theoretical and Fundamental Chemistry |
In 1804, Dalton explained his atomic theory to his friend and fellow chemist Thomas Thomson, who published an explanation of Daltons theory in his book A System of Chemistry in 1807. According to Thomson, Daltons idea first occurred to him when experimenting with "olefiant gas" (ethylene) and "carburetted hydrogen gas" (methane). Dalton found that "carburetted hydrogen gas" contains twice as much hydrogen per measure of carbon as "olefiant gas", and concluded that a molecule of "olefiant gas" is one carbon atom and one hydrogen atom, and a molecule of "carburetted hydrogen gas" is one carbon atom and two hydrogen atoms. In reality, an ethylene molecule has two carbon atoms and four hydrogen atoms (CH), and a methane molecule has one carbon atom and four hydrogen atoms (CH). In this particular case, Dalton was mistaken about the formulas of these compounds, and it wasnt his only mistake. But in other cases, he got their formulas right. The following examples come from Daltons own books A New System of Chemical Philosophy (in two volumes, 1808 and 1817):
Example 1 — tin oxides: Dalton identified two types of tin oxide. One is a grey powder that Dalton referred to as "the protoxide of tin", which is 88.1% tin and 11.9% oxygen. The other is a white powder which Dalton referred to as "the deutoxide of tin", which is 78.7% tin and 21.3% oxygen. Adjusting these figures, in the grey powder there is about 13.5 g of oxygen for every 100 g of tin, and in the white powder there is about 27 g of oxygen for every 100 g of tin. 13.5 and 27 form a ratio of 1:2. These compounds are known today tin(II) oxide (SnO) and tin(IV) oxide (SnO). In Daltons terminology, a "protoxide" is a molecule containing a single oxygen atom, and a "deutoxide" molecule has two. Tin oxides are actually crystals, they dont exist in molecular form.
Example 2 — iron oxides: Dalton identified two oxides of iron. There is one type of iron oxide that is a black powder which Dalton referred to as "the protoxide of iron", which is 78.1% iron and 21.9% oxygen. The other iron oxide is a red powder, which Dalton referred to as "the intermediate or red oxide of iron" which is 70.4% iron and 29.6% oxygen. Adjusting these figures, in the black powder there is about 28 g of oxygen for every 100 g of iron, and in the red powder there is about 42 g of oxygen for every 100 g of iron. 28 and 42 form a ratio of 2:3. These compounds are iron(II) oxide (FeO) and iron(III) oxide (FeO). Dalton described the "intermediate oxide" as being "2 atoms protoxide and 1 of oxygen", which adds up to two atoms of iron and three of oxygen. That averages to one and a half atoms of oxygen for every iron atom, putting it midway between a "protoxide" and a "deutoxide". As with tin oxides, iron oxides are crystals.
Example 3 — nitrogen oxides: Dalton was aware of three oxides of nitrogen: "nitrous oxide", "nitrous gas", and "nitric acid". These compounds are known today as nitrous oxide, nitric oxide, and nitrogen dioxide respectively. "Nitrous oxide" is 63.3% nitrogen and 36.7% oxygen, which means it has 80 g of oxygen for every 140 g of nitrogen. "Nitrous gas" is 44.05% nitrogen and 55.95% oxygen, which means there are 160 g of oxygen for every 140 g of nitrogen. "Nitric acid" is 29.5% nitrogen and 70.5% oxygen, which means it has 320 g of oxygen for every 140 g of nitrogen. 80 g, 160 g, and 320 g form a ratio of 1:2:4. The formulas for these compounds are NO, NO, and NO.
The earliest definition of Dalton's observation appears in an 1807 chemistry encyclopedia:
Dalton's atomic theory garnered widespread interest but not universal acceptance shortly after he published it because the law of multiple proportions by itself was not complete proof of the existence of atoms. Over the course of the 19th century, other discoveries in the fields of chemistry and physics would give atomic theory more credence, such that by the end of the 19th century it had found universal acceptance. | 0 | Theoretical and Fundamental Chemistry |
The quest for new elements is usually described using atomic numbers. As of , all elements with atomic numbers 1 to 118 have been observed. Synthesis of new elements is accomplished by bombarding target atoms of heavy elements with ions, such that the sum of the atomic numbers of the target and ion elements equals the atomic number of the element being created. In general, the half-life of a nuclide becomes shorter as atomic number increases, though undiscovered nuclides with certain "magic" numbers of protons and neutrons may have relatively longer half-lives and comprise an island of stability.
A hypothetical element composed only of neutrons has also been proposed and would have atomic number 0, but has never been observed. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the Cahn–Ingold–Prelog (CIP) sequence rules (also the CIP priority convention; named after Robert Sidney Cahn, Christopher Kelk Ingold, and Vladimir Prelog) are a standard process to completely and unequivocally name a stereoisomer of a molecule. The purpose of the CIP system is to assign an R or S descriptor to each stereocenter and an E or Z descriptor to each double bond so that the configuration of the entire molecule can be specified uniquely by including the descriptors in its systematic name. A molecule may contain any number of stereocenters and any number of double bonds, and each usually gives rise to two possible isomers. A molecule with an integer describing the number of stereocenters will usually have stereoisomers, and diastereomers each having an associated pair of enantiomers. The CIP sequence rules contribute to the precise naming of every stereoisomer of every organic molecule with all atoms of ligancy of fewer than 4 (but including ligancy of 6 as well, this term referring to the "number of neighboring atoms" bonded to a center).
The key article setting out the CIP sequence rules was published in 1966, and was followed by further refinements, before it was incorporated into the rules of the International Union of Pure and Applied Chemistry (IUPAC), the official body that defines organic nomenclature, in 1974. The rules have since been revised, most recently in 2013, as part of the IUPAC book Nomenclature of Organic Chemistry. The IUPAC presentation of the rules constitute the official, formal standard for their use, and it notes that "the method has been developed to cover all compounds with ligancy up to 4... and… [extended to the case of] ligancy 6… [as well as] for all configurations and conformations of such compounds." Nevertheless, though the IUPAC documentation presents a thorough introduction, it includes the caution that "it is essential to study the original papers, especially the 1966 paper, before using the sequence rule for other than fairly simple cases."
A recent paper argues for changes to some of the rules (sequence rules 1b and 2) to address certain molecules for which the correct descriptors were unclear. However, a different problem remains: in rare cases, two different stereoisomers of the same molecule can have the same CIP descriptors, so the CIP system may not be able to unambiguously name a stereoisomer, and other systems may be preferable. | 0 | Theoretical and Fundamental Chemistry |
A LIFT measures photosynthesis by exposing the plant to short flashes of blue light and analyzing the changes in fluorescence over time by the help of the FRR technique. | 0 | Theoretical and Fundamental Chemistry |
Carbon dioxide, a key reactant in photosynthesis, is present in the atmosphere at a concentration of about 400 ppm. Most plants require the stomata to be open during daytime. The air spaces in the leaf are saturated with water vapour, which exits the leaf through the stomata in a process known as transpiration. Therefore, plants cannot gain carbon dioxide without simultaneously losing water vapour. | 0 | Theoretical and Fundamental Chemistry |
Marguerite Catherine Perey (19 October 1909 – 13 May 1975) was a French physicist and a student of Marie Curie. In 1939, Perey discovered the element francium by purifying samples of lanthanum that contained actinium. In 1962, she was the first woman to be elected to the French Académie des Sciences, an honor denied to her mentor Curie. Perey died of cancer in 1975. | 1 | Applied and Interdisciplinary Chemistry |
Hydroperoxides are intermediates or reagents in major commercial processes. In the cumene process, acetone and phenol are produced by decomposition of cumene hydroperoxide (Me = methyl): | 0 | Theoretical and Fundamental Chemistry |
Dispersing trace amounts of nanoparticles into common base fluids has a significant impact on the optical as well as thermo physical properties of base fluid. This characteristic can be used to effectively capture and transport solar radiation. Enhancement of the solar irradiance absorption capacity leads to a higher heat transfer resulting in more efficient heat transfer as shown in figure 2.
The efficiency of a solar thermal system is reliant on several energy conversion steps, which are in turn governed by the effectiveness of the heat transfer processes. While higher conversion efficiency of solar to thermal energy is possible, the key components that need to be improved are the solar collector. An ideal solar collector will absorb the concentrated solar radiation, convert that incident solar radiation into heat and transfer the heat to the heat transfer fluid. Higher the heat transfer to fluid, higher is the outlet temperature and higher temp lead to improved conversion efficiency in the power cycle.
nanoparticles have several orders of magnitude higher heat transfer coefficient when transferring heat immediately to the surrounding fluid. This is simply due to the small size of nanoparticle. | 0 | Theoretical and Fundamental Chemistry |
* Wilfried Umbach (Hrsg.), Kosmetik und Hygiene von Kopf bis Fuß, Wiley-VCH Verlag GmbH & Co. KGaA, 3. vollst. überarb. u. erw. Auflage (2012), . | 0 | Theoretical and Fundamental Chemistry |
The lost-wax casting process may also be used in the production of cast glass sculptures. The original sculpture is made from wax. The sculpture is then covered with mold material (e.g., plaster), except for the bottom of the mold which must remain open. When the mold has hardened, the encased sculpture is removed by applying heat to the bottom of the mold. This melts out the wax (the wax is lost) and destroys the original sculpture. The mold is then placed in a kiln upside down with a funnel-like cup on top that holds small chunks of glass. When the kiln is brought up to temperature (1450-1530 degrees Fahrenheit), the glass chunks melt and flow down into the mold. Annealing time is usually 3–5 days, and total kiln time is 5 or more days. After the mold is removed from the kiln, the mold material is removed to reveal the sculpture inside. | 1 | Applied and Interdisciplinary Chemistry |
It has long been known that filamentous cyanobacteria perform surface motions, and that these movements result from type IV pili. Additionally, Synechococcus, a marine cyanobacteria, is known to swim at a speed of 25 μm/s by a mechanism different to that of bacterial flagella. Formation of waves on the cyanobacteria surface is thought to push surrounding water backwards. Cells are known to be motile by a gliding method and a novel uncharacterized, non-phototactic swimming method that does not involve flagellar motion.
Many species of cyanobacteria are capable of gliding. Gliding is a form of cell movement that differs from crawling or swimming in that it does not rely on any obvious external organ or change in cell shape and it occurs only in the presence of a substrate. Gliding in filamentous cyanobacteria appears to be powered by a "slime jet" mechanism, in which the cells extrude a gel that expands quickly as it hydrates providing a propulsion force, although some unicellular cyanobacteria use type IV pili for gliding.
Cyanobacteria have strict light requirements. Too little light can result in insufficient energy production, and in some species may cause the cells to resort to heterotrophic respiration. Too much light can inhibit the cells, decrease photosynthesis efficiency and cause damage by bleaching. UV radiation is especially deadly for cyanobacteria, with normal solar levels being significantly detrimental for these microorganisms in some cases.
Filamentous cyanobacteria that live in microbial mats often migrate vertically and horizontally within the mat in order to find an optimal niche that balances their light requirements for photosynthesis against their sensitivity to photodamage. For example, the filamentous cyanobacteria Oscillatoria sp. and Spirulina subsalsa found in the hypersaline benthic mats of Guerrero Negro, Mexico migrate downwards into the lower layers during the day in order to escape the intense sunlight and then rise to the surface at dusk. In contrast, the population of Microcoleus chthonoplastes found in hypersaline mats in Camargue, France migrate to the upper layer of the mat during the day and are spread homogeneously through the mat at night. An in vitro experiment using Phormidium uncinatum also demonstrated this species' tendency to migrate in order to avoid damaging radiation. These migrations are usually the result of some sort of photomovement, although other forms of taxis can also play a role.
Photomovement – the modulation of cell movement as a function of the incident light – is employed by the cyanobacteria as a means to find optimal light conditions in their environment. There are three types of photomovement: photokinesis, phototaxis and photophobic responses.
Photokinetic microorganisms modulate their gliding speed according to the incident light intensity. For example, the speed with which Phormidium autumnale glides increases linearly with the incident light intensity.
Phototactic microorganisms move according to the direction of the light within the environment, such that positively phototactic species will tend to move roughly parallel to the light and towards the light source. Species such as Phormidium uncinatum cannot steer directly towards the light, but rely on random collisions to orient themselves in the right direction, after which they tend to move more towards the light source. Others, such as Anabaena variabilis, can steer by bending the trichome.
Finally, photophobic microorganisms respond to spatial and temporal light gradients. A step-up photophobic reaction occurs when an organism enters a brighter area field from a darker one and then reverses direction, thus avoiding the bright light. The opposite reaction, called a step-down reaction, occurs when an organism enters a dark area from a bright area and then reverses direction, thus remaining in the light. | 0 | Theoretical and Fundamental Chemistry |
Highly contaminated drinking water has been detected at several locations in Sweden. Such locations include Arvidsjaur, Lulnäset, Uppsala and Visby. In 2013, PFAS were detected at high concentrations in one of the two municipality drinking water treatment plants in the town of Ronneby, in southern Sweden. Concentrations of PFHxS and PFOS were found at 1700 ng/L and 8000 ng/L, respectively. The source of contamination was later found to be a military fire-fighting exercise site in which PFAS containing fire-fighting foam had been used since the mid-1980s.
Additionally, low-level contaminated drinking water has also been shown to be a significant exposure source of PFOA, PFNA, PFHxS and PFOS for Swedish adolescents (ages 10–21). Even though the median concentrations in the municipality drinking water were below <1 ng individual PFAS/L, positive associations were found between adolescent serum PFAS concentrations and PFAS concentrations in drinking water. | 0 | Theoretical and Fundamental Chemistry |
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